Plasma arc torches are commonly used for cutting, marking, gouging, and welding metal workpieces by directing a high energy plasma stream consisting of ionized gas particles toward a workpiece. The plasma arc torch is typically connected to a power supply that provides both gas and electric power for operation of the plasma arc torch and is operable through a trigger disposed within a torch handle for activation of the gas and the electric power. With plasma arc torches of the known art, the trigger operates both the gas and the electric power such that neither the gas nor the electric power are controlled separately local to the torch handle. Some known art plasma arc torches provide separate gas controls, however, the controls are disposed within the power supply or at a location remote from the operator.
Activation of gas flow only, i.e. no electric power, is often advantageous in certain applications such as for cooling torch parts or the workpiece. However, many plasma arc devices do not provide for a gas only mode of operation, and those that do provide for such a mode require the operator to initiate and terminate the gas flow at the power supply, or at another remote location, not local to the plasma arc torch where operations are being performed. As a result, operation of a gas only mode is relatively time consuming and cumbersome in plasma arc torch systems of the known art.
Additionally, with plasma arc torches of the known art, a few seconds typically elapse from the time an operator engages a trigger to when a plasma stream is generated, which is a function of the amount of time required for the gas to travel from the power supply, through the torch lead, and to the torch head. Accordingly, with longer torch leads, the restart times are correspondingly longer, which results in further delays that reduce work efficiency and that can become frustrating to an operator if the torch is shut off and re-ignited on a regular basis. In one known system, a gas control valve is provided that dissipates gas in a plasma arc chamber after a plasma arc has been extinguished. However, the gas must still travel the length of a torch lead and rise gradually in accordance with the teachings of the known system.
Accordingly, a need remains in the art for a device and method that more efficiently controls the flow of gas to a plasma arc torch. A further need exists for such a device and associated method that reduces restart times, that is relatively simple to operate, and that does not require significant manual dexterity of the operator.